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Employee Benefit Plans (Benefit Cost Components) (Details) - CAD ($) | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Pension Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Service Cost | $ 51,000,000 | $ 49,000,000
Defined Benefit Plan, Interest Cost | 95,000,000 | 99,000,000
Defined Benefit Plan, Expected Return on Plan Assets | 138,000,000 | 129,000,000
Defined Benefit Plan, Amortization of Gains (Losses) | (33,000,000) | (38,000,000)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit) | (1,000,000) | 0
Current year amortization of regulatory asset liabilities | 26,000,000 | 17,000,000
Settlement, curtailment | 4,000,000 | (1,000,000)
Net Periodic Benefit Cost, Total | 70,000,000 | 73,000,000
Non-pension Benefit Plans [Member |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Service Cost | 6,000,000 | 5,000,000
Defined Benefit Plan, Interest Cost | 13,000,000 | 14,000,000
Defined Benefit Plan, Expected Return on Plan Assets | 2,000,000 | 3,000,000
Defined Benefit Plan, Amortization of Gains (Losses) | 1,000,000 | (2,000,000)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit) | 0 | (8,000,000)
Current year amortization of regulatory asset liabilities | (2,000,000) | (1,000,000)
Settlement, curtailment | 0 | 0
Net Periodic Benefit Cost, Total | $ 14,000,000 | $ 9,000,000

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- Definition Amount of (increase) decrease in accumulated benefit obligation of defined benefit plan from effects of settlement and curtailment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (r) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(4) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(5) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of cost recognized for passage of time related to defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of net periodic benefit cost (credit) for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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